Method of making metallic articles



1945- J. A. MERRYMAN ETAL 2,390,805

METHOD OF MAKING METALLIC ARTICLES Filed March 10, 1943 WITNESSESI-INVENTORS @"WC' (3 James A. Merry/71cm &

foward M Wharffiur.

0 ATTORNEY Patented Dec. 11, 1945 METHOD OF MAKING METALLIC ARTICLESJames A. Merryman and Edward M. Wharif,-Jr., Wilkinsburg, Pa., assignorsto Westinghouse Electric Corporation, East Pittsburgh, Pa., acorporation of Pennsylvania Application March 10, 1943, Serial No.478,642

2 Claims.

This invention relates to the method of producing metallic articles.

It is an object of this invention to provide a method of producingstrong articles of spray metal.

Another object of this invention is to increase the strength of articlesof spray metal without increasing the size of the article.

Other objects of this invention will become a parent from the followingdescription when taken in conjunction with the accompanying drawing, inwhich:

Figure 1 is a view in elevation of a shaft having a worn end.

Fig. 2 is a view in elevation and partly in section of the shaft of Fig.1 having spray metal applied thereto in accordance with the teachings of.this invention.

Fig. 3 is an end View in section of the shaft of Fig. 2 with the layersof spray metal carried thereon, V

Fig. 4 is an end view in section of the shaft carrying the spray metalafter it has been subjected to a heat treatment in accordance with theteachings of this invention.

Fig. 5 is a view in section of apparatus illustrating the application ofthe teachings of this invention for the making of articles utilizing aremovable form.

Fig. 6 is a photomicrograph at a magnification of 250 times of spraymetal steel, and

Fig. 7 is a photomicrograph at a magnification of 250 times of the spraymetal of Fig. 6 after having been treated in accordance with theteachings of this invention.

In accordance with this invention, metallic articles are produced bypracticing the method of constructing the articles and heat treatingthem as explained more fully hereinafter. In industry, many metallicarticles such as shafts or the like have worn surfaces which render'such articles unsatisfactory for further service.

Likewise, many castings have pits or flaws therein which render thecasting unsatisfactory but which, if filled with a strong bonding metal,can be used commercially.

Referring to Fig. 1 of the drawing, there is illustrated a shaft l0having a worn end or surface l2. In accordance with this invention, theworn surface 12 is roughened as by knurling or otherwise abrading itafter which metal similar to the metal of the shaft lll'is sprayedthereon to deposit a layer M of spray metal of predetermined thicknessas illustrated in Figs. 2 and 3.

I2, the spray metal mechanically links or interlocks with the roughenedsurface and is retained thereon. The spray metal deposit 14 can bereadily controlled as to thickness, shape and size, the resultingstructure being porous and having an oxide coating'formed on theinterlocking portions of the spray metal. When tested, such a deposit ofspray metal is found to have only about half of the tensile strength ofthe solid metal before it is sprayed.

- After the layer Id of spray metal is deposited, the article carryingthe spray metal is preferably heat treated in a reducing atmosphere ofhydrogen or a mixture of hydrogen and nitrogen or other suitablereducing atmosphere to effect the reduction of the oxides formedduringthe spraying of the deposit [4. The lengthof time of heat treating thedeposit in the reducing atmosphere to remove the oxides therefrom willvary depending upon the amount of oxides which are present.

When thus heat treated, a suitable brazing metal such as copper, or thewell known copper base brazing alloys, or the like, are applied to theoxide-free deposit of spray metal. A preferred method of applying thebrazing metal is to spray a layer It of the brazing metal over theexternal surface of the treated layer I 4. The amount of brazing metalthus applied depends upon the thickness of the layer [4 as will be moreapparent from the description given hereinafter.

After the layer I6 of brazing metal is applied to the layer l4, theshaftv l0 carrying the spray metal is admittedto a brazing furnace (notshown) and is heated to a temperature above the melting point of thebrazing material but beto applying the layer l6.

low the melting point of the sprayed metal I and the shaft It) in areducing atmosphere, and maintained at such temperature for a sufficientlength of time to permit the brazing material to completely impregnatethe layer l4 and bond to the surface I2 of the shaft In as illustratedin Fig. 4. Upon examination it is found that the impregnated layer It isthe same as it was prior In other words, the brazing metal does notincrease or otherwise change the size of the layer [4 when it fills thepores thereof.

By effecting-the impregnation in a reducing atmosphere, all oxidespresent in the layers of spray metal are effectively reduced andcomplete impregnation is obtained if the layer I6 of brazing metal is ofa thickness sufficient for supplying enough of the brazing metal forsuch impregnation. Of course, an excess of brazing metal is a wasteremaining on the surface of the layer M or flowing therefrom in thefurnace. Any excess of the brazing metal remaining on the surface of thelayer I4 can be readily machined Preferably the article is then cooledin the repound as sprayed.

When treated as described hereinbefore and, impregnated with copper,thepsteel has an en- 250 times.

difierent thicknesses of the layer M for obtaining the completeimpregnation of the layer l4 and the bonding to the surface I! of theshaft 10.

In another embodiment of this invention, the layer i4 oi spray metal isapplied to a' removable form is as illustrated in Fig. 5 ofthe drawing.In this embodiment the form I8 is of graphite or other suitablerefractory material, and is designed to have the predetermined shape andsize of the article which is to be produced. The layer i4 is readilysprayed onto the form It to any predeterminedthickness and is thereaftertreated in a reducing atmosphere to effect the reduction of any oxides.In this embodiment the brazing metal may be applied to thelayer H as byspraying as de'scribed with respect to the embodiment shown in Figs. 1through 4, or the brazing metallin the form of the pellets 20 or'thelike may be positioned on the layer ll as illustrated in Fig. 5.,The pellets 20 mayv thus be positioned while the coated form is. in thereq ducing atmosphere, the temperature of the furnace then beingincreased to a temperature above the melting point of the brazing metaland maintained at such temperature to insure the complete impregnationof the porous metal layer H.

ducing atmosphere to below 200 C. to prevent the formation of oxides.When thus formed, the impregnated layer ll is readily stripped from thetherefrom. By the optimum and minimum thickness of the layer it can bedetermined for where the sprayed steel is not completely impregnated, aremarkable improvement in strength is obtained, for, in another articlein which insumcient copper was employed for-impregnating the sprayedmetal, the strength of the'brazed-spray metal increased from onefoot-pound to ifootpounds when impregnated even though the article had aporous structure.

form "to give a strong article of required shape and size.

In actual practice, it may be preien'ed to apply a thicker layer-l4 -ofthe spray metal than is actually required, and after impregnating thelayer M with the-brazing metal to machine the impregnatedv layer to theexact. size of the required article. This can readily be' accomplishedas the impregnated layer can be as readily ma- I chined as the basemetal. Referring to Figs."6 and lot the drawin there is illustratedphotomicrographs of sprayed steelof the type 01' the layer l4 and of thesame steel after having been impregnated with copper.

Fig.6 in particular is a photomicrograph at a magnification of 250 timesof sprayed SAE steel #1010, and clearlyillustrates the eiiect ofspraying the steel in that'inipurities are included and the steel isdeposited substantially in layers.

Such sprayed steel, when subjected to the Izod impact test, had astrength of only one footutilized as the brazing material completely im-7 'pregnates the porous structure of the sprayed steel. The impregnatedsprayed steel illustrated in Fig. 7 has an Izod impact strength 0150footthe impregnated sprayed steel over the steelas. sprayed-isremarkableand clearly illustrates the pounda Such improvement in the strength ofvalue of the present invention, similar results being obtained in othersprayed articles.

In general, the impregnation of the sprayed metal layer can befficiently effected by subjecting the sprayed metal to a temperature ofbetween 1900 and 2100" F. in a reducing atmosphere for a period of timeof from 1 to 2 hours to insure the removal of oxides,.'and, after thecopper or other brazing material is applied to the oxidefree sprayedmetal, subjectingthe article to a temperature of between 2000 and 2300F. in the reducing atmosphere for a period of time of from 10 minutes to1% hours, depending upon the size of the article.. I

This invention is particularly applicable to the reclaiming of shafts,tools or-the like which have been damaged in service, or to castingswhich have pits and flaws or chips therein. The portions of the articlewhich have been rebuilt by applying the spray metal and treated inaccordance with this invention have unusual strength and makes itpossible to utilize the articles in industry where otherwise they wouldbe normally discarded.

Although this invention has been described with reference to aparticular embodiment thereof, it is, of course, not to be limitedthereto except in so far as is-necessitated by the scope of the appendedclaims.

We claim as our invention:

1. The method of making metallic articles comprising, in combination,spraying low carbon steel to deposit and form a. spray metal articlehaving a porous structure, heating the sprayed steel to a temperature ofbetween1900 F. and 2100" F/in a reducing atmosphere for a period of timeranging from one to two hours to reduce anyqoxides present thereon,applying a brazingmetal selected from the group consisting of copper andcopper base alloys to the heat treated article, and subjecting thearticle to a temperature of between 2000' F. and 2300? F. in a reducingatmosphere for a period of time sumcient to permit the brazing metal topenetrate and substantially fill the pores of the sprayed steel.

2. The. method of. making metallic articles comprising, in combination,spraying low carbon steel to deposit and form aspray metal articlehaving a porous structure, heating the sprayed steel to'a temperature ofbetween 1900 F. and 2100 F. in a reducing atmosphere for a period oi.time rangin from one to two hours to reduce any oxides presentthereon,spraying a brazing metal selected from the group consisting of cop perand copper base alloys onto the heat treated sprayed steel, andsubjecting the sprayed composite metal to a temperature of between-2000F.

to penetrate and substantially fill the pores oithe sprayed steel. Y yJAMES A.,MER.RYMAN.

EDWARD M. Jr...

